Apparatus for connecting and disconnecting and/or threading and unthreading tubular members such as pipe joints and the like is widely used. And, in particular, such apparatus is readily utilized in the drilling industry for the purpose of connecting and disconnecting sections of pipe and other elongated elements such as drill pipe, well casing, production tubing, sucker rods, etc., all herein generically referred to as pipe. During drilling, completion and servicing operations for deep wells such as are typically drilled for the production of petroleum products, lengths of pipe are interconnected by connecting operations for developing a string of pipe that is run into the well for the purposes intended. Further, upon removal of a string of pipe from the well it is necessary to break out the individual joints of pipe as the pipe string is withdrawn from the well. During making up and breaking out operations, it is desirable to provide power energized equipment that is capable of applying relatively high torque to the pipe joints, especially during breakout operations. In the petroleum industry, such power energized devices are typically referred to as power tong assemblies and these power tong assemblies have become quite well developed over the years.
In most cases, pipe tong devices incorporate teeth capable of biting into the outer surface of the pipe to establish a gripping relationship therewith. Such pipe engaging teeth are typically formed on inserts that are referred to as "dogs," and are driven into biting, pipe deforming relationship with a high degree of force. In many cases, the dogs of pipe tongs are driven by means of power energized cams and other mechanical force amplifying means to ensure the development of positive gripping relationship with the pipe in order to cause the pipe to rotate during application of high torque forces thereto.
It is well known that stress will materially weaken section of pipe under circumstances where the pipe is scored severely during handling operations such as thread makeup and breakout. Further, the forces applied by power tong devices can also cause substantial crushing of the pipe to occur and can result in stress fractures that materially detract from the functional capability of the pipe involved. It is desirable, therefore, to provide a power energized mechanism for makeup and breakout of threaded pipe connections having the capability of applying substantial torque to the pipe and yet which effectively prevents scoring or crushing of the pipe so that the inherent strength of the pipe remains substantially unchanged as the result of any makeup and breakout operations. Further, since pipe is frequently reused a number of times in the drilling, completion and servicing of wells, it is highly desirable to minimize any damage to the pipe that might be caused during thread makeup and breakout operations by the means of pipe tongs, thus providing for extended service life of the pipe.